This invention relates to heating, ventilation, and air conditioning (HVAC) equipment, and is more particularly related to combustion systems and heat exchangers for furnaces.
Combustion systems such as furnaces generate noise because, by necessity, there are gases flowing in and around the burner and the heat exchanger of the furnace. In some instances, the sound level may be high enough to be unpleasant or unacceptable. In such systems, the combustion process itself is a dominant factor in the generation of noise. Normally, this arises because of the turbulent flow of the combustion air and of the combusting fuel-and-air mixture. It is not always possible to arrange the heat exchanger assembly, furnace cabinet, and other components to reduce the generation of noise to a satisfactory low level. For example, in an induced draft combustion furnace that has a plurality of side-by-side heat exchangers, each with a monoport inshot burner, it is difficult to design a noise reduction system which would not lower the efficiency of the furnace, raise the level of NOx gases, or make the size of the components inordinately bulky.
Also, in an induced-draft inshot-burner type of furnace, it is highly desirable to have an even heating of the first or inlet course of the heat exchanger. That is, the metal walls of the heat exchanger are typically aluminized, and can suffer cracking or structural weakening if there are hot spots and ensuing thermal stressing in the heat exchanger walls.